Method of treating waste-activated sludge using electroporation

ABSTRACT

A system that allows the flexibility of primary and secondary treatment of municipal sludge, paper-pulp sludge, animal and plant waste, whereby the treatment thereof via electroporation may be used either as the primary dewatering treatment, secondary dewatering treatment, direct WAS-treatment, and combinations with other conventional dewatering techniques, in order to provide the municipal treatment plant, or the paper-pulp treatment plant, with the most cost-effective and efficient system as possible. The electroporated-treated sludge releases hitherto unreleased biosolids exiting from the PEF-electroporation system, which are returned to aeration tanks. The electroporation process causes the release of intracellular dissolved/organic matter, which is used as “food” for the bacteria of the aeration tanks.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This is a continuation-in-part application of application serialNo. 09/468,42.7, filed on Dec. 21, 1999.

BACKGROUND OF THE INVENTION

[0002] In applicant's copending application serial number, there isdisclosed a system and method for dewatering and treatingwaste-activated sludge (WAS) emanating from municipal waste, orpulp-waste from a paper mill, as well as treating animal and plantwaste. In that application, the method for breaking down the WAS is tosubject the WAS to electroporation, which incorporates nonarcing,cyclical high voltages in the range of between 15 KV and 100 KV, whichbreak down inter-cellular and intracellular molecular bonds, to thusrelease inter-cellular and intracellular water, whereby the WAS isrendered inactive and greatly reduced in mass.

[0003] In said above-noted copending application, the apparatus andmethod disclosed therein, while capable in certain circumstances ofbeing a primary municipal-sludge treatment, its intended and mainobjective was to use it as a secondary treatment to previously-dewateredmunicipal waste sludge. It is the goal of the present invention to adaptthe method and apparatus of said copending application serial No.09/468,427 into a main, primary treatment of municipal waste sludge.

[0004] In a previous (Phase I) project, it has been demonstrated thelaboratory feasibility of pulsed electric field (PEF) for disrupting thebiomass in waste activated sludge (WAS) derived from municipalwastewater treatment. While there was no significant increase in thesolids content of dewatered sludge, the quantity of WAS needing disposalwas estimated to be significantly reduced.

[0005] Encouraged by the Phase I results, a pilot plant for testing atone or two wastewater treatment plants that generate WAS has beendeveloped. It has been decided that a pulsed electric field (PEF) systemthat could handle 0.5 to 1.0 pgm WAS feed be designed. This requires an8 kw power supply capable of generating 30 kV and pulse generatorcapable of handling 50 amp peak, current, bi-polar pulses, square wave,10 μs pulse width, and 3000 pulses/second (pps).

SUMMARY OF THE INVENTION

[0006] It is the primary objective of the present invention to provide amethod and apparatus for dewatering municipal waste sludge, paper-pulpwaste sludge, animal and plant waste, using electroporation for theprimary treatment of the sludge.

[0007] It is also a primary objective of the present to provide such asystem that will allow flexibility as to the primary and secondarytreatment of municipal sludge, paper-pulp sludge, animal and plantwaste, whereby the treatment thereof via electroporation may be usedeither as the primary dewatering treatment, secondary dewateringtreatment, direct WAS-treatment, and combinations with otherconventional dewatering techniques, in order to provide the municipaltreatment plant, or the paper-pulp treatment plant, with the mostcost-effective and efficient system as possible.

BRIEF DESCRIPTION OF THE DRAWING

[0008] The invention will be more readily understood with reference tobe accompanying drawings, wherein:

[0009]FIG. 1 is a schematic showing the electroporation system as usedas a secondary dewatering treatment;

[0010]FIG. 2 is a schematic showing the electroporation system used inconjunction as a primary dewatering treatment in accordance with thepresent invention;

[0011]FIG. 3 is a schematic showing the electroporation sub-system foruse in dewatering municipal, paper-puklp, animal and plant wastesludges; and

[0012]FIG. 4 is a schematic diagram showing the overall apparatus of thepresent invention incorporating the electroporation sub-system for useas a primary or secondary dewatering treatment;

DETAILED DESCRIPTION OF THE INVENTION

[0013] The original concept for the pulsed-electric filed (PEF) effectusing electroporation was to dewater the reviously-dewatered sludge.However, additional PEF data on a paper plant sludge has indicated thatthe big PEF effect from electroporatior of WAS occurs at higher energylevels (e.g., 100 J/mL; or 400 k Wh/ton (DS) for feed at 6 percentsolids), whereby cells are disrupted. The result is inactivation ofcells, breakage of cells and release of some intracellulardissolved/organic matter and typically a worsening of flocculation anddewatering. Therefore, a more effective way of using this process is torecycle all of the PEF-treated sludge back to a aerobic bioreactor toutilize the sludge as food; that is, it has been discovered that thePEF-electroporation effect on disrupting the cellular units of the WAShas been to release intracellular dissolved/organic matter. Thisintracellular dissolved/organic matter is just the type of ideal “food”upon which the aerobic bioreactor flourishes. Thus, returning thisreleased intracellular dissolved/organic matter back to the aerobicbioreactor will increase the BOD load on the bioreactor, and will thusreduce the quantity of WAS by up to about 50 percent. The flowsheet forthis scenario is shown in FIG. 2. Thus, it is now practical to employthe PEF-electroporation system as not only a secondary system fortreating previously-dewatered sludge, but also to employ it as a primarysystem, as described hereinbelow.

[0014] Referring to FIG. 1, there is shown the schematic for using thePEF-electroporation system as a secondary treatment forpreviously-dewatered sludge, as disclosed in Applicant's copendingapplication serial No. 09/468,427. In FIG. 1, the wastewater isdelivered to the primary treatment, aerobic-reactor tanks 10, and fromto a secondary clarifier 12. From there, the WAS is delivered to thePEF-electroporation system 14 of the invention for deactivating the WASto make it a Class “B” biomass for easier disposal. The biomass is thensent to a belt press 16 for further processing and disposal.

[0015] Referring now to FIG. 2, there is shown the flow chart of thepresent invention for employing the PEF-electroporation system as partof the primary treatment. In this system, the biosolids exiting from thePEF-electroporation system 14 are returned to the aeration tanks 10,since, as explained above, the PEF process causes the release ofintracellular, dissolved organic matter, which is used as “food” for thebacteria of the aeration tanks. This “food” not only is further treatedin the aeration tanks via aerobic digestion, but actually causes theaerobic digestion process in the aerobic tank itself to be acceleratedfor the same amount of oxygen supplied.

[0016] A practical problem with the system of FIG. 2 is that the PEFthroughput needs to be of the same order of magnitude as the WASdisposal rate in order to see a noticeable effect of PEF on WASreduction. For this reason a 1.8 ton (DS)/day PEF system has been chosenas a pilot plant. With such a system, a WAS reduction of 0.9 ton/day ona dry basis or 7.5 tons/day on a filter press cake (at 12 percentsolids) basis may be achieved. In terms of thickened sludge (at 2percent solids) basis, this translate to elimination of 45 tons/dayneeding to be flocculated and dewatered. This will require PEF treatmentof 15 gpm WAS at 2 percent solids.

[0017] One way to reduce the cost of the pilot plant, which is driven bythe PEF power supply and pulser cost, is to pre-thicken the WAS.Therefore, a 15 gpm rental centrifuge 18 is used for pilot testing. Itis estimated that this will produce a 5 gpm feed for the PEF reactor ata solids content of 6 percent. Such a feed can be handled by a Moynopump. The feed streams to the centrifuge and the PEF units arerepresented as Stream Nos. 10 and 11, respectively in FIG. 2. However,in practical application such as centrifuge may not be necessary.

Pef Power Supply and Pulser Design

[0018] The conceptual design of the power supply and the pulse generator(pulser) for the system of FIG. 2 is shown in FIG. 3. This figure showsfour chambers 20 in series, although two chambers also can be used ifthe pulse rate is increased. The specifications for the two-chamberdesign are shown in Table 1. The design requires a 35 kW input powersupply 22 (32 kW continuous output) delivering 30 kV. The pulsegenerator 24 is 200 amp maximum current and a pulse rate of 4,000 hz.(maximum). TABLE 1 Pilot Plant PEF Power Supply, Reactor, and PulserChambers Gap Distance D (cm) 1.2 Chamber 1 Number of chambers in use 2Flow Conditions Flow rate (ml/s) 315 PEF Parameters Voltage to apply(kV) 30 Rep-rate (pps) 3342.254 Pulse duration (μs) 4 PhysicalProperties Conductivity (S/m) 0.2 Density (g/cm³) 1 Specific Heat ([J/(g· ° C.)] 4.18 Viscosity (Pa · s) 0.0100 Dosage Level Electric FieldStrength (kV/cm) 25 Total Treatment Time (μs) 80 Number of pulses perchamber 10 Temperature Change Temperature increase per pair of chamber(° C.) 11.962 Related Information Residence Time (s) 0.00299 Flow Speed(cm/s) 401.070 Energy Consumption (J/ml) 100 Estimated Power requirement(W) 31500 Reynolds Number 4010.705 Pulse Generator Current 78.5

[0019] The actual sludge handling system and the associatedinstrumentation is shown in FIG. 4. A detailed list of specifications isprovided in Table 2. Tank T1 holds up to 100 gallons of untreated feedmaterial, delivered through valve V1 from the centrifuge 18. A mixer isprovided for blending infeed material. A bottom drain allows disposal tosewer at the end of a test run. Valve V4 is provided for withdrawing asample for analysis. Material leaves T1 through V2 and a strainer to avariable-speed progressing cavity pump, which can flow from 0.5 to 5.0gallons per minute. The tank, pump mixer and associated valves aremounted to one 42-inch square skid for transport purposes. The feedleaving P1 passes through quick-connect fittings to a reinforced hose tothe reactor.

[0020] The PEF-electroporation reactor subsystem includes a powersupply, pulse generator and pairs of treatment chambers as describedabove with reference to FIG. 3. These would be mounted to a skid , alongwith associated valves V5, 6 and 7. Quick-connect fittings and hoseconvey the treated material to valves on the outlet tank skid. ValvesV12 and 13 permit the treated material to be recycled back to T1. ValveV8 permits the treated material to enter tank T2, of 100-galloncapacity. As with T1, a mixer, a sample port and a bottom drain areprovided. Tank T2, pump P2, mixer M2 and associated valves are mountedto another skid. Treated material leaving through V10 leads to transferpump P2. Valve V18 is a globe style for adjusting the flow rate throughV14 to tank T3. Valve V13 allows treated material from T2 to return toT1, assisted by P2, to increase treatment time.

[0021] The P2 pump is used to return the treated sludge to thebiotreatment plant, aerobic tanks 10, when the PEF-electroporationsystem is used as a primary system, or optionally to filter press 16, ifdesired, when the PEF-electroporation system is used as a secondarytreatment.

[0022] Safety logic has been incorporated as follows. Level control L1will close V1 to prevent overfilling T1, with subsequent spillage. Levelcontrol L2 will shut down P1 and the power supply when the liquid levelbecomes too low. Level control L3 and T2 will shut down P1 and the powersupply when tank T3 becomes full, to prevent spillage. TABLE 2 SludgeHandling System Specifications Description Supplier Qty Inlet Tank T1100-Gal carbon steel jacketed mixing tank 1 Buckeye Fab. 1 2-inch PVC,Schedule 80 90-Deg. elbow, 806-020 (bypass in) Harrington Mixer, 1C-Clamp mount direct drive, ¼ HP, 400-250-DD-ED Harrington 2 Union ballvalve, 2-inch socket, 1001020 Harrington 1 Strainer, 2-inch clear PVC,RVAT108 Harrington 1 Replacement screen, PVC Harrington 1 2-inch PVC,Schedule 80 pipe, 800-020, 20 feet length Harrington 2 2-inch PVC,Schedule 80 90-Deg elbow, 806-020 Harrington 2 Quick disconnect, Part F,2-inch, polypro., FPP-020 Harrington 2 Quick disconnect, Part C, 2-inch,polypro., CPP-020 Harrington 100 ft Hose, PVC standard duty, 2-inch,110P-020 Harrington 10/pack Hose clamps, 3-inch, H-44SS Harrington 1Bulkhead fitting, ½-inch PVC BF10050SXT Harrington 1 Ball valve, ½-inchsocket, 107005 Harrington 1 Elbow, 90-degree, ½-inch Sch 80 Pvc, 806-005Harrington 1 Level control, high to shut feed valve, LV751 Omega 1 Levelcontrol, low to shut off pump P1 and Powr supply, LV751 Omega 1 Solidstate relay for feed valve, SSR240AC10 Omega 1 Solid state relay forpump and power supply, SSR240AC25 Omega 1 Feed Valve V1 Quickdisconnect, Part F, 2-inch, polypro., FPP-020 Harrington 1 Quickdisconnect, Part C, 2-inch, polypro., CPP-020 Harrington 1 Union ballvalve, 2-inch, 1001020 Harrington 1 Electric actuator, 2085020Harrington 1 Process Pump P1 Pump, 5.0 down to 0.5 GPM, 35 psi, MoynoBuckeye Pump 1 Direct Current control for pump, NEMA 4 enclosure BuckeyePump 2 Hose nipples, polypro., 2-inch, HNPP-020 Harrington 2 2-inch PVC,Schedule 80 tee, 801-020 Harrington 1 2-inch PVC, Schedule 80 pipe,800-020, 20 feet length Harrington 2 2-inch PVC, Schedule 80 90-Degelbow, 806-020 Harrington 2 Reactor Connections Quick disconnect, PartF, 2-inch, polypro., FPP-020 Harrington 2 Quick disconnect, Part C,2-inch, polypro., CPP-020 Harrington 1 Union ball valve, 2-inch socket,1001020 Harrington 2 2-inch PVC, Schedule 80 socket tee, 801-020Harrington 2 Reducing bushing, 2-inch by ½-inch thread, 838-247Harrington 2 ½-inch by 1-1/2-inch long PVC Schedule 80 nipple, 882-015Harrington 2 Union ball valve, ½-inch threaded, 1001005 Harrington 1½-inch PVC Schedule 80 threaded tee, 805-005 Harrington 2 Reducingbushing ½-inch to ¼-inch threaded, 839-072 Harrington 1 Pressure gaugewith guard, 0-60 psig, GGME060-PP Harrington 2 Tube adapter, ¼-inch MPTto ¼-inch tube, 4MSC4N-B Parker Outlet Tank T2 1 100-Gal jacketed carbonsteel tank with legs, 2-in outlet Buckeye Fab. 1 2-inch PVC, Schedule 8090-Deg elbow, 806-020 (inlet) Harrington Union ball valve, 2-inch socket1001020 Harrington 3 Quick disconnect, Part F, 2-inch, polypro., FPP-020Harrington 3 Quick disconnect, Part C, 2-inch, polypro., CPP-020 3Harrington 4 2-inch PVC, Schedule 80 90-Deg elbow, 806-020 Harrington 22-inch PVC, Schedule 80 socket tee, 801-020 Harrington 3 2-inch PVC,Schedule 80 threaded tee, 805-020 Harrington 2 2-inch by 6-inch PVC,Schedule 80 nipple Harrington 1 Mixer, C-Clamp mount direct drive, ¼ HP,400-250-DD-ED Harrington 1 ½-inch by 2-inch PVC, Schedule 80 Harrington1 Ball valve, ½ inch socket, 107005 Harrington 1 Elbow 90-degree, ½-inchSch 80 PVC, 806-005 Harrington 1 Level control, low to shut off pump P1and Powr supply, LV751 Omega 1 Solid state relay for pump and powersupply, SSR240AC25 Omega Outlet Tank Pump Pump, 5 GPM 20 feet of head,centrifugal 1 Buckeye Pump Motor starter, NEMA 4 with thermal unit 1C.E.D. Hose nipples, polypro., 2-inch, HNPP-020 4 Harrington 1 Glovevalve, threaded, PVC, 2-inch, 1261020 Harrington Product Pump P2 Pump, 5GPM 20 feet of head, centrifugal 1 Buckeye Pump Motor starter, NEMA 4with thermal unit 1 C.E.D. Sealtite, ½-inch lot C.E.D. Wires, cords lotC.E.D. Skids 42-inch square, metal, fork lift entry four sidesInstrumentation Oscilloscope, storage, two inputs, 100 MHz, 1 printerinterface Tektronix 1 Current sensor, 0.01 Volt/Ampere, 100 Amp. max.Pearson Electr. 1 Clamp-on flowmeter, 2 to 12-inch pipe, 4-20 ma outputControlotron 1 Voltage sensor, 60 Kilovolt, 1000 v/1V, Type PVM-1 NorthStar Resch 1 Printer, Epsom jet Model 740, Part No. C257001 parallelport ADS Systems 1 Centronics-type paraller printer port cost, EpsomF2E020-06 ADS Systems 1 ea. Type K thermocouple readout, Omega DP45KF +SB45 Omega 2 Type K thermocouple, 304SS sheath, 1/8-in. dia.,KQSS-18G-12 Omega 1 Conductivity and pH meter, 0-200 μS, 0-14 pH,P-19651-20 Cole-Parmer 2 Conductivity and pH flow-through cell,P-19502-42 Cole-Parmer Alternative clamp-on flow meter, Omron FD-303 +FD-5 sensor for ¼-in. to ¾-in. pipe + FD-5000 sensor for ¾-in. to 12-in. pipes.

[0023] While a specific embodiment of the invention has been shown anddescribed, it is to be understood that numerous changes andmodifications may be made therein without departing from the scope andspirit of the invention as set forth in the appended claims.

What I claim is:
 1. A method of dewatering paper-pulp sludge, municipalwaste sludge, animal waste sludge containing intra-cellular watermolecules contained in molecular cellular units of the waste sludge, orplant and animal waste sludge, comprising: (a) pumping the waste sludgeinto a dewatering apparatus; (b) destroying in the dewatering apparatusat least most of the individual cellular units of the waste sludge inorder to release the intra-cellular water molecules contained therein;and said step (b) causing massive disruption of the cellular matter,allowing for the release of bound as well as intra-cellular liquids andintracellular dissolved/organic matter, which may be used as food forthe bacteria of aeration tanks; (c) directing the released intracellulardissolved/organic matter to an aeration tank for supplying food tobacteria of said aeration tank.
 2. The method according to claim 1,wherein said said step (b) comprises electroporating said sludge.
 3. Themethod according to claim 2, wherein said electroporation is performedwith voltages between 15 KV. ad 100,00 KV.
 4. A method of treatingsludge, such as paper-pulp sludge, municipal sludge, plant and animalwaste, in which the sludge is treated in an aeration tank for performingaerobic digestion, comprising: (a) treating the sludge to a dewateringprocess that releases intracellular dissolved/organic matter; (b)directing the sludge treated in said step (a) to an aeration tank forperforming aerobic digestion thereon whereby the intracellular,dissolved organic matter is used as food for the bacteria of theaeration tanks, whereby the aerobic digestion process is acceleratedthereby for the same amount of supplied oxygen.
 5. The method accordingto claim 4, wherein said step (a) comprises electroporating the sludge.6. The method according to claim 4, further comprising alternativelydirecting the sludge directly to a further dewatering process.
 7. Amethod of treating sludge, such as paper-pulp sludge, municipal sludge,plant and animal waste, (a) treating the sludge to a dewatering processthat releases intracellular, dissolved organic matter; (b) directing thesludge treated in said step (a) to one of: an aeration tank forperforming aerobic digestion thereon, or to a different, dewateringprocess.
 8. The method according to claim 7, wherein said step (b)comprises alternatively directing the sludge to further dewateringprocess consisting of a filter press.
 9. The method according to claim7, wherein said (b) comprises directing the sludge to an aeration tank,where said intracellular, dissolved organic matter is used as food forthe bacteria of the aeration tanks, whereby the aerobic digestionprocess is accelerated thereby for the same amount of supplied oxygen.